(560ap) Esterification of Isobutyl Alcohol and Acetic Acid - Kinetic Study

Currently there is an increasing pressure at the chemical industry to generate safer and environmentally friendly products. As a results the industry is experiencing a change in the production paradigms, following a transition from fossil-based to biobased products. In particular, this is a major trend in the segment of organic solvents. Several green solvents, which have been identified according to sustainability criteria, are gaining pace at the industrial scale for their good performance and reduced impacts. Among these, esters of fermentation-derived alcohols and acids are of particular interest because their broad range of applications. From this group, isobutyl acetate standouts as an excellent solvent for coatings, inks, lacquers, and cosmetic products (e.g. nail polish). Also, it is a valuable ingredient in the perfumery, flavors and fragrances industry for its fruity aroma.

Entirely biobased Isobutyl acetate can be produced by esterification of isobutyl alcohol (obtained from fusel oil) and acetic acid (from vinegar fermentation). The process involves an acid catalyst as reaction promoter, and because the need for suitable sensory properties, most traditional homogeneous catalysts cannot be used because they affect the organoleptic profile (odor and color). Thus, focusing on the required organoleptic profile for the fine chemicals industry, the use of heterogeneous catalysts (e.g. ion exchange resin) would be preferred. Taking into account that the reaction conversion is limited by the chemical equilibrium, the implementation of a reactive distillation process would enable higher conversions and savings in product purification. However, in order to explore the usefulness of a reactive distillation process for isobutyl acetate production, there is need to develop the corresponding kinetic model.

Thus, this work focused on the kinetic study of the Fisher esterification between isobutanol and acetic acid, using Amberlyst 15 and sulfuric acid as catalyst. Preliminary experiments helped to rule out mass transfer limitations during experiments, and the Weiss-prater criteria was used as surrogate for ensuring kinetic regime. Experiments were carried out based upon a suitable experimental design including temperature, mole ration of reactants and catalyst loading as main variables. Additional experiments were carried out to evaluate chemical equilibrium constant at different temperatures. The whole set of experimental data were correlated with mole fraction and activity-based kinetic expressions; the last to account for non-idealities of the reactive mixture. Both models fitted well with experiments, and can be used for further design of a reactive distillation process.